Added gzip support

MPExtended will compress the response if the Accept-Encoding header includes gzip
Added X-Original-URL check

When MPExtended is behind a proxy it needs to know what the original URL was so web stream results can be set correctly
Added EditSchedule

WebMediaPortal uses two operations (DeleteSchedule + AddSchedule) to simulate an edit. This makes it possible to do the same thing in one operation which is important if you're making the request remotely.